A novel self-aligned technique for 0.15 ?m gate length AlInAs-GalnAs HEMTs has been demonstrated. Devices with an oxide sidewall yielded an fT of 177 GHz whereas devices with no sidewall exhibited an fT greater than 250 GHz.
The difference has been related to process damage during plasma deposition of SiO2. An extrinsic fT of 292 GHz was measured at 77K.